Since an organic Electro Luminescence (EL) element is a self-light-emitting element of a current driven type, the need for a backlight is eliminated while the advantage of low-power consumption, high viewing angle, high contrast ratio or the like is obtained; it is expected to perform well in the development of a flat panel display.
In an organic EL display device using such an organic EL element, subpixels of different colors of red (R), green (G) and blue (B) are used to constitute a large number of pixels, which makes it possible to display various kinds of color images. While these subpixels of R, G, and B (RGB) may be located in various different forms, they are generally arranged in stripes by equally placing subpixels of different colors (so-called RGB vertical stripe arrangement), as illustrated in FIG. 1. All colors can be displayed by adjusting the brightness among the three subpixels. In general, adjacent three subpixels of R, G and B are collectively regarded as one rectangular pixel, and such rectangular pixels are arranged in a square to realize a dot matrix display. In the display device of a dot matrix type, image data to be displayed has a matrix arrangement of n×m. A correct image can be displayed by associating the image data with each pixel one for one.
Furthermore, organic EL display devices have different structures including a color filter type which creates the three colors of RGB with a color filter on the basis of a white organic EL element, and a side-by-side selective deposition type which deposits different colors on the respective organic EL materials for the three colors of RGB using Fine Metal Mask (FMM). While the color filter type has a disadvantage in that the light use efficiency is lowered as the color filter absorbs light, resulting in higher power consumption, the side-by-side selective deposition type can easily have wider color gamut due to its high color purity and can have higher light use efficiency because a color filter is eliminated, thereby being widely used.
Here, it is important for a display device such as an organic EL display device or a liquid crystal display (LCD) device to have enhanced resolution, and thus various methods of devising the arrangement of subpixels have been proposed to improve native resolution. For example, as to a liquid crystal display device, a method has been proposed for improving native resolution by utilizing the characteristic of human eye which senses G or Y (Yellow) brighter than R or B and constituting one pixel with four subpixels including Y in addition to RGB, so as to have two peak values of luminance in one pixel. Another method has also been proposed in which one pixel is constituted by subpixels of four colors including W (White) in addition to RGB. Furthermore, a rendering method with the configuration of subpixels of four colors such as RGBY or RGBW has also been disclosed. Moreover, as to an organic EL display device, for example, Woo-Young So et al., SID 10 DIGEST 43.3 (2010) (hereinafter referred to as Document 1) discloses a method of constituting one pixel with subpixels of four colors including R, G, B1 (light blue) and B2 (deep blue) as illustrated in FIG. 2.